Electrical conductivity in a flooring system is desirable to minimize the potential for generating and/or maintaining an electrostatic charge on the floor. The ability of a floor to generate an electrostatic charge is referred to as tribocharging. The ability of the human body to tribocharge by movement across a floor has been further defined as Body Voltage Generation (BVG). It is generally desirable to minimize the ability of floors to tribocharge. In some environments it can be critical because electrostatic charges as low as 50 volts can damage sensitive equipment.
Body Voltage Generation occurs on antistatic flooring as well as insulative flooring. The function of an antistatic floor coating is to minimize the ability of the floor to tribocharge and to bleed off any charge that is created as quickly as possible. The type of fillers used determine the ability of a floor coating to control BVG and to bleed off any charges generated. Currently, the two principal types of antistatic coating systems are particulate systems and fiber systems. Particulate floor coating systems are highly loaded with conductive particles. As a result, they utilize the entire coating surface to conduct away the electric charge. These systems do a good job of limiting BVG, typically permitting less than 15 volts of BVG to be generated. In addition, particulate systems bleed off the charge almost instantaneously. Fiber systems are generally less effective than particulate systems because they employ oriented conductive fibers, thereby limiting the amount of points that will conduct the electrical charge away. Fiber systems can generate in excess of 100 volts of BVG. Not only do these systems allow higher BVG to generate, they also take longer to bleed off the charge. Under low humidity, fiber based coating systems may never bleed off the charge entirely.
Both of the foregoing systems have their limitations. Particulate systems are easy to install but are expensive, making their use in thick coatings cost prohibitive. Fiber systems are inexpensive but difficult to install. The fibers must be aligned perpendicular to the surface and, if misaligned, the antistatic floor will not function properly. In addition, the current coatings are frequently not durable enough for manufacturing environments and are subject to loss of adhesion to the substrate. The loss of adhesion is caused by moisture vapor transmission through the concrete of the floor to the interface of the concrete and coating. Typically, only thick troweled systems have the ability to withstand this moisture at the interface because of greater surface preparation and increased bond and peel strength. Since cost typically limits the thickness of particulate systems, they can rarely be employed at thicknesses necessary to eliminate the problem of adhesion loss caused by moisture vapor transmission. Still further, the conductive fillers typically used in both fiber and particulate systems tend to make the coatings softer with less cohesive strength. The products currently available have raw material costs that make the installation of thick coatings, for example in excess of 90 mils, cost prohibitive.
There has been a need for antistatic coating systems that are more durable in manufacturing environments, can be applied in greater thicknesses and that resist moisture vapor transmission. An antistatic coating combining the conductive performance and ease of installation of a particulate system, with the lower cost of a fiber system, but which does not exhibit the drawbacks of either, is needed in the industry.